The present invention relates to a scroll machine of a full rotation type in which both a driving scroll and a driven scroll are rotated.
FIG. 5 is a cross section of a conventional scroll machine such as disclosed in Japanese Kokai No. 87693/1987, in which a reference numeral 1 depicts a casing, 2 a flange arranged in the casing 1 and having vertical oil return holes 2a and 3 a bearing support fixedly secured to the flange 2 and having a central, cylindrical boss portion 3a. A reference numeral 4 depicts a motor having a motor shaft 4a whose upper end is rotatably supported within the boss portion 3a. An eccentric hole 4b is formed in the upper end of the motor shaft 4a and an oil supply path 4c formed in the shaft 4a extends therealong to establish a communication from the eccentric hole 4b to the lower end of the shaft 4a. A reference numeral 5 depicts a driving scroll having a shaft 5a inserted into the eccentric hole 4b, 6 a stationary scroll coupled to the bearing support 3 to form, together with the driving scroll 5, a compression chamber 7, 8 a trochoid pump arranged between a lower surface 4d of the eccentric hole 4b and a lower end 5b of the shaft portion 5a and coupled to the latter. The trochoid pump has a suction port 4e formed in the bottom 4d of the eccentric hole 4b and a discharge port 5c formed in the lower end 5b of the shaft portion 5a. A reference numeral 9 depicts lubricant oil reserved in a bottom portion of the casing 1 in which the lower end of the motor shaft 4a is immersed A known anti-rotation mechanism 10 is provided for preventing rotation of the driving scroll 5. Reference numerals 13 and 15 depict a discharge port for discharging gas from the casing 1 and a suction port communicated with a space between the scrolls 5 and 6, respectively.
In operation, when the motor shaft 4a rotates, the driving scroll 5 orbits with respect to the stationary scroll 6, so that gas is taken in from the suction port 15, compressed by means of the relative movement of the stationary scroll 6 to the driving scroll and discharged through the discharge port 13 outside of the casing 1. With the rotation of the motor shaft 4a having the eccentric hole 4b in which the shaft portion 5a of the driving scroll 5 is received, the shaft portion 5a tends to rotate eccentrically together with the driving scroll 5. However, due to the presence of the anti-rotation mechanism 10 provided between the driving scroll 5 and the bearing support 3, the shaft portion 5a orbits. Therefore, the trochoid pump 8 disposed between the shaft portion 5a and the bottom 4d of the eccentric hole 4b performs a pump operation with an aid of an inner surface of the eccentric hole 4b, so that oil 9 is sent from the oil supply path 4c through the suction port 4e and the trochoid pump 8 to the discharge port 5c to lubricate sliding portions such as an outer periphery of the shaft portion 5a and the lower surface of the driving scroll 5 and, then returned through the oil return hole 2a to the bottom portion of the casing 1.
That is, in the conventional scroll machine, the oil pump portion is arranged at the upper end of the motor shaft and oil in the bottom portion of the casing has to be sucked up through the oil supply path formed in the motor shaft. Therefore, the length of the oil supply path becomes large, necessarily, causing fluid resistance in the suction side of pump to be large and the size of pump to become large.